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Subject[PATCH AUTOSEL 5.1 085/219] selinux: fix empty write to keycreate file
Date
From: Ondrej Mosnacek <omosnace@redhat.com>

[ Upstream commit 464c258aa45b09f16aa0f05847ed8895873262d9 ]

When sid == 0 (we are resetting keycreate_sid to the default value), we
should skip the KEY__CREATE check.

Before this patch, doing a zero-sized write to /proc/self/keycreate
would check if the current task can create unlabeled keys (which would
usually fail with -EACCESS and generate an AVC). Now it skips the check
and correctly sets the task's keycreate_sid to 0.

Bug report: https://bugzilla.redhat.com/show_bug.cgi?id=1719067

Tested using the reproducer from the report above.

Fixes: 4eb582cf1fbd ("[PATCH] keys: add a way to store the appropriate context for newly-created keys")
Reported-by: Kir Kolyshkin <kir@sacred.ru>
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
security/selinux/hooks.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 614bc753822c..bf37bdce9918 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -6269,11 +6269,12 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
} else if (!strcmp(name, "fscreate")) {
tsec->create_sid = sid;
} else if (!strcmp(name, "keycreate")) {
- error = avc_has_perm(&selinux_state,
- mysid, sid, SECCLASS_KEY, KEY__CREATE,
- NULL);
- if (error)
- goto abort_change;
+ if (sid) {
+ error = avc_has_perm(&selinux_state, mysid, sid,
+ SECCLASS_KEY, KEY__CREATE, NULL);
+ if (error)
+ goto abort_change;
+ }
tsec->keycreate_sid = sid;
} else if (!strcmp(name, "sockcreate")) {
tsec->sockcreate_sid = sid;
--
2.20.1
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